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Skin treatment with photodynamic therapy

Carol Coley
RN BSc(Hons)
Skin Cancer Nurse Specialist
Portsmouth Hospital NHS Trust

Photodynamic therapy (PDT) is a form of photochemotherapy in which the interaction between a photosensitiser, visible light and oxygen leads to a photo-oxidative reaction within the targeted cells.(1) PDT is recommended for the treatment of lesions that are unsuitable for other available therapies due to possible complications and/or poor cosmetic outcome.(2)
PDT can be used to treat nonmelanoma skin cancers and is a relatively noninvasive treatment that can easily be run as a nurse-led service. At present PDT is only carried out in hospitals, but in the future it could be carried out by an experienced dermatology-trained nurse in a community health centre under the supervision of a dermatologist.

Which patients are suitable for PDT?
A consultant dermatologist will decide which patients will benefit most from PDT depending on the result of a biopsy taken from the lesion. PDT is most effective for treating cutaneous malignancies, for example those arising from Bowen's disease (BD), solar keratoses (also known as actinic keratoses) and superficial basal cell carcinomas (BCCs). All treatment options are discussed with the patient during the consultation.(3) Photographs of the lesion are taken to provide an accurate record pre- and post-treatment.

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How does PDT work?
Before treatment the PDT room will be prepared with all the equipment required, eg, a skin marker to mark out the lesion, gauze, a gallipot, normal saline solution sachets, film dressings and a suitable surgical dressing such as Mepore (Mölnlycke Health Care). The PhotoCure Aktilite lamp was specifically developed for use as a light source for PDT, and is used in combination with Metvix cream. The Aktilite lamp is an LED lamp that emits visible red light of certain wavelengths. This red light has the ability to effectively penetrate human tissue and is therefore also effective for thicker lesions. The Metvix cream is applied topically to the lesion and left to work for approximately three hours, allowing the active ingredient to be absorbed into the target cells. The active ingredient in the Metvix cream is methylaminolevulinate, which accumulates selectively in the diseased cells. When the skin lesion is illuminated with red light from the Aktilite lamp, a molecular reaction occurs that results in the destruction of cancer cells.(2,4) The Cynosure Smartcool cooling system provides blasts of cold air that can be positioned over or around the area during the treatment. It has six cooling levels and can be adjusted according to the patient's needs. This helps to reduce the burning sensation caused by the reaction of the Metvix cream with the red light during irradiation.

Softening agent
The lesion may have a crust that needs to be removed to enable the Metvix cream to properly penetrate. In this situation the patient will be asked to apply a softening agent to the lesion for a few weeks before treatment, for example, 2% salicylic acid in white soft paraffin. On the day of treatment, the crust can be removed by using forceps (if the lesion will come off easily), or by using a disposable scalpel or curette (if it is more adherent). These instruments will need to be available in the PDT room. Any congealed blood will need to be removed as this can also reduce the penetration and efficacy of the sensitising cream and the activating light.(3)

The treatment
The nurse will need to explain all aspects of the treatment to the patient to ensure that the patient understands what to expect. It is recognised that patients with a good knowledge of their disease or procedure have a better outcome than those who do not.(5) The patient is then prepared for application of the photosensitising agent. The site and size of the lesion and the time of application of the cream are all recorded by the nurse on the treatment sheet.

Cleansing
Depending on the site of the lesion the patient is either positioned on a couch or in a chair. The lesion is cleansed with normal saline solution and any crust is removed. The Metvix cream is applied to the lesion, approximately 1mm thick and with a 5mm margin around the lesion. An adhesive film dressing is then applied to keep the Metvix cream in place and prevent leakage. A Mepore dressing or gauze swab is secured on top of the film dressing to occlude light to the lesion. The Metvix cream is left on for three hours. The patient can either stay in the department or go out and return at an agreed time.

Irradiation
After three hours, the lesion site is ready to be irradiated. The dressings are removed and the Metvix cream is washed off using a swab moistened with normal saline. The room light is switched off and a Woods UVA lamp is shone on the lesion site. The fluorescence seen is an indicator of the degree of uptake of the Metvix cream and can be used to help delineate the tumour margins where clinical margins are indistinct.(3) Any fluorescence should be noted on the patient's documentation. When the Woods UVA lamp is shone on the lesion it appears as a red/pink area. The room light is then turned on again. The lesion is now ready to be treated.

Light source
The nurse places the Aktilite light source approximately 8cm over the lesion. Healthy surrounding skin does not need to be protected from the light source, as only the diseased cells absorb the cream. This means that the surrounding skin is unaffected by the treatment and therefore scarring is minimal. The patient and the nurse wear protective goggles for the duration of the light treatment, as the red light is uncomfortable to look at. The light treatment usually lasts for about eight minutes. It is important that the patient remains in the same position for the duration of the light treatment to ensure that the lesion has maximum exposure. The Cynosure Smartcool fan is positioned to ensure that the area being treated is cooled. Most patients find that the Cynosure Smartcool fan helps with pain management.

Is PDT painful?
The level of discomfort experienced during PDT varies from patient to patient. Most patients tolerate the treatment without analgesia.1 Pain usually occurs in the early part of the light exposure, peaking within minutes and then levelling out during the remainder of exposure.(6)
Morton argues that pain relief should be given before treatment as waiting for pain to occur is too late.(7) Topical lignocaine may be sprayed onto the area before irradiation. Most patients find that the Cynosure Smartcool fan helps to alleviate the pain. Patients can take paracetamol for pain relief, and some centres use Entonox (gas and air; BOC Medical) and topical lidocaine patches (which provide local pain relief for 12 hours) as alternative methods. Gambles et al point out that there are a number of factors that help to predict the severity of pain. They suggest that the scalp is the most sensitive site, that large lesions are usually more painful than smaller ones, that solar keratoses tend to be more painful than lesions due to BD and superficial BCCs, and that men tend to experience more pain than women.(8)
It is sometimes necessary to administer local anaesthetic (1% plain lignocaine) to a lesion site if the patient feels the treatment is too painful. However, it is worth remembering that injecting lignocaine can be just as painful as the treatment. By talking to the patient the nurse should be able to assess their discomfort during the treatment, giving them reassurance and something else to focus on. The treatment may be paused at any time during the light irradiation if the patient is unable to tolerate the pain.

Post-treatment care
After the PDT treatment a moisturising cream is applied to the treated area and a light occlusive dressing such as a Mepore dressing applied over the top. This dressing should be kept on for 24 hours to prevent any further light uptake by the lesion. The moisturising cream helps to soothe the treated area. Locoid Lipocream (hydrocortisone butyrate; Yamanouchi) is given to the patient in case they have a blistering reaction after treatment. Locoid Lipocream will help to treat any localised oedema and/or erythema that may occur post-treatment. Local oedema and erythema usually occur for about a day after the light exposure, but may last for several days, particularly if multiple sites on the face have been treated.(9) The patient is advised to take a simple analgesic if they experience any further pain.
 
Follow-up
If the patient is being treated for BD or superficial BCCs they will need to return for further treatment a week later. At this point they should be questioned on any reactions to their last treatment. Patients being treated for solar keratoses need just one treatment. All patients should be given a three-month follow-up appointment with the consultant to assess the success of the treatment. Generally, when patients return for their follow-up appointments, they are very pleased by the cosmetic outcome.
In our department we treat patients with Gorlin's syndrome (a genetically determined syndrome) on a rolling three-monthly programme. Patients with Gorlin's are more prone to develop multiple BCCs. These patients are very pleased with the cosmetic results after PDT. Before PDT their treatment option would have been either cryotherapy (liquid nitrogen) or surgical excision. We have also treated patients with metastatic breast cancer, where PDT has been used to good effect to help control the chronic itching and skin irritation they can experience. PDT is currently being used in other centres to treat conditions such as viral warts and acne.

Conclusion
PDT can be used to successfully to treat solar keratoses, lesions associated with BD and superficial BCCs. The overall cosmetic results for PDT are excellent, and it has been suggested that by targeting specific cells for destruction PDT is fundamentally sounder than using cryotherapy or excising what can only be seen with the eye.(8)
Although photodynamic therapy is not a pain-free treatment, it is a noninvasive treatment that could be provided as a nurse-led service.

References

  1. von Felbert V, Braathen LR. Developments in photodynamic therapy. Hosp Pharm Eur 2003;10:33-5.
  2. DermNet NZ. Photodynamic therapy (PDT) - patient information. Available from http://www.dermnetnz.org/dna.phototherapy/pdt.html
  3. Smith B, Rossi S, Buick L. Hands on topical PDT. Dermatol Nurs 2002;1:12-3.
  4. Metvix(®)  - methyl aminolevulinate: information for prescribers, purchasers and health service providers. Langley: Galderma (UK) Ltd; 2003.
  5. Mills ME, Sullivan K. The importance of information giving for patients newly diagnosed with cancer: a review of the literature. J Clin Nurs 1999;8:631-42.
  6. Morton CA, Brown SB, Collins S, et al. Guidelines for topical photodynamic therapy: a report of a workshop of the British Photodermatology Group. Br J Dermatol 2002;146:552-67.
  7. Morton C. Photodynamic therapy for nonmelanoma skin cancer - and more. Arch Dermatol 2004;140:116-22.
  8. Gambles B, Anste A, Edwards C. Nursing management of patients undergoing photodynamic therapy (PDT). Torfaen: Gwent Healthcare NHS Trust; 2000.
  9. Suthamjariya K, Taylor CR. Photodynamic therapy for the dermatologist. Available from http://www.emedicine.com/derm/topic636.htm

Resources
British Association of Dermatologists
W:www.bad.org.uk
Galderma UK
W:www.galderma.co.uk

Further reading
Rhodes LE, et al. Photodynamic therapy using topical methyl aminolevulinate vs surgery for nodular basal cell carcinoma. Arch Dermatol 2004; 140:17-23
 Freeman M, et al. A comparison of photodynamic therapy using topical methyl aminolevulinate (Metvix) with single cycle cryotherapy in patients with actinic
keratosis: a prospective, randomized study. J Dermatol Treatments 2003; 14:99-106
Solar AM, et al. A follow-up study of recurrence and cosmesis in completely responding superficial and nodular basal cell carcinomas treated with methyl 5-amino-laevulinate-based photodynamic therapy alone  and with prior curettage. Br J  Dermatol 2001; 145:467-71